Caterpillar D8 with Cable Operated Blade


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Caterpillar D8, picture 1

Features

  • Left and right crawler each driven by a micromotor
  • Hand powered cable operated blade

It all started with the idea to build a giant stripping shovel. Because I succeded and created a 1 / 28 scale model of The Mountaineer, there was a need for an auxiliary dozer to assist the shovel. Of course, it had to be in the same scale.

Caterpillar D8, picture 2

When talking about dozers, Caterpillar is a synonym. Therefore my model can be found in Caterpillars product range of the early fifties. The Mountaineer went into service in 1956, so I opted for a 1951 D8 with a cable operated No. 8A blade.

Caterpillar D8, picture 3

When the stripping shovel was finished there were still two micromotors left. Unfortunately, I had used nearly all chain links of the newer type on the shovel so that the crawlers of the dozer are made of old style chain links with two studs on each link. To fit the scale, the crawlers had to be three studs wide which I realized by attaching 1 x 3 plates on every link. The crawlers run over a set of two old style 9 tooth gears each. To hide the red gears, yellow wedge belt wheels sit on the same axles. The rear gear on each side is driven by a micromotor via a set of new bevel gears.

Caterpillar D8, picture 4

The fact that the two micromotors are powered independently allows the model not only to move in a straight direction but also allows negotiating curves and turn on place. Unfortunately the motors are a bit weak and there is not enough space in the model to implement a reduction gear. Therefore the dozer can only be operated on flat surfaces, it won't climb grades.

Caterpillar D8, picture 5

At the time the prototype of my model was built, hydraulics were not yet that common as they are today. Therefore crawler tractors often featured one ore two winches which were used to operate several tools like a scraper drawn by the tractor or a dozer blade which turned a crawler tractor into a bulldozer. My model features two winches at its back end. One of them carries the rope which is used to adjust the height of the blade above or below ground. The second winch is connected to the first one and is used to operate this one by means of rotating it manually.
The rope runs along the lenght of the machine in a pipe. At the front end it feeds a pulley which sits atop the grille and has its counterpart on the blade. This way, the blade can be lifted or lowered by reeling the rope in or out.

Caterpillar D8, picture 6

Beside these major functions, my model features several details found also on the real dozer. First there is a six cylinder in-line engine complete with exhaust pipe, air and oil filters. All the levers needed to control the movement of the machine and the winches can be found as well. Last but not least, there is a driver. Because the model is in 1 / 28 scale it was not possible to use a standard minifig. Therefore I only took the head and built the body with basic bricks.

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